The present invention relates generally to the implantation of stent prostheses in body lumens and to delivery systems for transporting and accurately deploying or releasing such stents. More specifically, the invention is directed to a mechanism method for delivering and deploying a self-expanding stent utilizing a fluid-operated containment and releasing system.
Auxiliary to surgical or other related invasive medicinal procedures, expandable stent implant devices are widely used in blood vessels, urinary tract ducts or other difficult to access places for the purpose of preventing restenosis, providing temporary or permanent vessel or lumen wall support or reinforcement and for other therapeutic or restorative functions. These devices are generally cylindrical or tubular in shape and are conveyed to a predetermined site or location of interest utilizing a vascular catheter, or similar transluminal device. In order to navigate the vascular system, the stents are delivered to the site constrained in a collapsed configuration or state of reduced diameter and are thereafter deployed by being released to expand or be expanded in situ. While temporary uses exist, these devices are generally designed as permanent implants which may become incorporated in the vascular or other tissue which they contact at implantation.
The stents are generally self-expanding or otherwise expanded in situ utilizing a fluid balloon or other such device. While the delivery and deployment system of the present invention can be adapted for use with either type of stent, the detailed embodiments illustrate deployment of the self-expanding variety. One well-known example of a type of self-expanding stent has become known as the Wallsten stent and is further illustrated and described in several issued U.S. patents, including Wallsten (U.S. Pat. No. 4,954,126); Wallsten (U.S. Pat. No. 4,655,771); and Wallsten et al (U.S. Pat. No. 5,061,275). (All documents cited herein, including the foregoing, are incorporated herein in their entirety for all purposes.) The Wallsten device is a woven device which has a flexible body formed of several individual flexible thread elements, each of which extends in a helix configuration with the center line of the body serving as a common axis. The elements are wound in the common direction but are displaced axially relative to each other and, under crossing a like number of elements also so axially displaced, but having the opposite direction of winding. This configuration provides a resilient braided tubular structure which assumes stable dimensions upon relaxation, but which elongates under axial tension with corresponding diameter contraction thereby enabling the stent to be mounted on a relatively small diameter catheter device and conveyed through the vascular system in a collapsed state or reduced diameter elongated configuration. As used herein, xe2x80x9cstentxe2x80x9d includes stent-graft and coated stents known in the art.
As indicated above, the delivery of these devices is generally accomplished by catheters of a class capable of delivering the stent to the site of interest, generally through the vascular system of the patient. Since this normally requires time consuming, torturous navigation to remote locations, improvements in the ability to accurately and easily deploy such stents once the site is reached are highly desirable.
Systems have been developed for remotely releasing the stents once the location of interest has been reached. One such system is illustrated and described in Euteneuer et al (U.S. Pat. No. 5,445,646) in which a delivery system for implantation of a self-expanding stent is disclosed which utilizes a retractable slipping sleeve system to expose a self-expanding stent held in a constrained position by bodily fluid-soluble retaining means which dissolve or swell to release the stent to radial expansion. The sleeves may be fluid operated.
While prior stent delivery systems have met with a degree of success, there remains a need for a system that will rapidly and accurately deploy a stent using distal, medial or proximal deployment. Using these terms, deployment or release is categorized according to the portion of the stent first released or expanded in situ. Delays necessitated by waiting for dissolution or expansion of retaining bands or other such constraint means require additional time which may allow unavoidable or undesirable movement of the stent, thereby reducing placement accuracy. Waiting for a delayed release system also extends the time required for the procedure.
Accordingly, it is highly desirable to provide a stent delivery system of the class described which increases the accuracy and reduces the time required for stent deployment and which, at the same time, makes the procedure easier for the operator and reduces the time required for the procedure.
It is a primary object of the present invention to provide a stent delivery and deployment system that permits rapid remote release of a stent in the location of interest.
Another object of the present invention is to provide an improved stent delivery and deployment system in which retractable deployment means also serves as the constraint means for the stent during transportation to the site of interest.
Yet another object of the present invention is to provide an improved stent delivery and deployment system which utilizes a self-retracting, extendable, improved fluid-operated release system.
Yet still another object of the present invention is to provide an improved stent delivery and deployment system which utilizes a collapsing bellows to operate the retracting device that serves as both constraint and deployment means.
Other objects and advantages of the present invention will occur to those skilled in the art upon familiarization with the descriptions and accounts contained in the specification.
By means of the present invention, there is provided a stent delivery and deployment system for procuring implantation of an expandable stent in a bodily lumen of interest. The catheter delivery and deployment system includes an elongate flexible catheter device designed to navigate the vascular system of a patient and to carry a stent retaining and deployment device attached toward the distal end of the catheter for deploying and expanding an expandable stent device, or possibly a stent-graft. The deployment system utilizes a fluid/operated retractable tubular sleeve system first as a containment or constraint device for initially retaining the stent on the catheter beneath the sleeve in a collapsed delivery configuration prior to release. Once properly aligned in situ, the tubular sleeve system is operable to retract from over the stent to release the stent distally, proximally or medially according to design of the system. In this manner, the stent can be positioned with accuracy; and at the beginning of release, should it be necessary, the stent can generally also be repositioned in the lumen.
In the detailed embodiments illustrating the invention, the catheter includes inner and outer co-axial tube members describing co-axial lumens and a constraint/release sleeve having a closed end slidably sealed about the outer co-axial tube and an open end through which a stent is released. The catheter connects proximally with a guidewire port and a fluid infusion port such that the inner co-axial lumen is a guidewire lumen and the outer lumen provides a fluid infusion lumen surrounding the inner tube.
In one embodiment, a first seal, or sliding seal, that is slidable along the outer catheter tube with respect to the sleeve is provided at the closed end of the sleeve sealing the inside of the sleeve to the outer catheter tube. A second seal, or stationary seal, that is stationary with respect to the catheter tubes, but slidable within the sleeve, is provided spaced from the first or sliding seal sealing the tube to the catheter and with the first seal defining a closed volume therebetween. The stent device is constrained by the sleeve portion extending beyond the stationary seal. Pressurized fluid infused from the outer lumen into the closed volume causes the volume to extend and the sleeve with the sliding seal to move away from the stationary seal and the stent thereby exposing and releasing the stent from the open end. The outer catheter tube may have infusion ports between the seals or it may end within the closed volume opening the lumen into the volume.
In an alternate embodiment, the outer catheter tube is connected to infuse into one or more extendable sealed bellows devices having one end which extends against a stop in the direction of the open end of the sleeve to urge the closed end of the sleeve in the opposite direction. As in the previous embodiments, the bellows can be configured to retract or collapse when the extended fluid pressure is released to urge the sleeve toward its original position in the manner of a double acting system.